DE2545684A1 - BACKFLOW SLIT FILTER - Google Patents

Abstract

The backwashing edge filter serves for removing solids in fluids. It is essentially composed of a screw-shaped spiral (1). The slots (2) between the individual turns act as a screen for the fluid (3). The slot width is adjustable from the outside by extending or compressing the spiral (1). <IMAGE>

Description

Backwash plate filter

The invention relates to a self-cleaning backwash gap filter to remove the solid fractions contained in a fluid.

"Fluid" is understood to mean gases or liquids.

The filter is particularly suitable for sampling for automatic Process analyzers to determine the gaseous or liquid sample from the contained therein To free solids fractions, as well as for the separation of solids fractions in the Gas or liquid phase in production systems. Such solid fractions are e.g. Dust, granules, fibrous particles or, especially in the case of liquids, solid deposits in the form of crystal sludge or crystallites etc. In analytical monitoring of fluids it is imperative that the fluid stream be cleaned beforehand, i.e. from Solids is freed. Otherwise there could be significant disruptions - specifically with continuously measuring automatic analyzers - occur. aside from that the devices would have to be serviced frequently.

Background of the Invention In cleaning fluid streams, a number of various continuous or discontinuous filter processes are used. These include filters with sieves, nets, etc. Such filters usually have to be cleaned be dismantled. This means a considerable expenditure of time and personnel. A solution to the problem is provided by filter belt devices, whereby the technical effort increases considerably.

Backwash filters are being used to an increasing extent. So far have been these filters are preferably used for the large-scale treatment of water.

Self-cleaning filters for analyzers have recently become commercial offered. In one embodiment, a discharge is made with the aid of a bypass flow of the deposited dirt (self-cleaning analyzer filter for Liquids and gases from Bühler & Co.). Another backwash filter consists of two identical filter elements and a backwash device (swirl clean - backflow filter system, publication no. 1006 from H. Maihak AG). Through the Backwashing, in which part of the sample water that has already been filtered through alternately one of the two filter elements is pushed back and by the bypass flow generated centrifugal effect, the filter surfaces of deposits largely kept free.

The filter devices described are in their field of application largely limited. Most of the time, the fluids supplied must be mechanical be pre-cleaned; d. H. the foreign matter must not exceed certain grain sizes. The degree of filtration can only be achieved by changing the insert, e.g. the filter membrane, changeable. The filter cleaning is associated with a lot of effort.

Most continuous measuring automatic analyzers are sensitive to contamination of the measuring system caused by solid substances can be. Numerous gas sampling probes are from different manufacturers in the Trade in order to remove these impurities from the measuring gas (e.g.

H. Karthaus, H. Engelhardt, physical gas analysis, basics, Publication L 3410 from Hartmann & Braun AG, Frankfurt, 1971, p. 7/8, p. 82/105 and Siemens pocket book for measurement and control in heating and chemical engineering, Munich, 1962). Ceramic filters are predominantly used today, either inside or outside an exhaust chimney is used (A. Naumann, extraction technology and other requirements for the successful use of analytical equipment, VDI reports No. 97, 1966, p. 39/49). These filters are designed to filter out soot flakes and coarse dust particles. Thereafter must the gas usually still be dried and finely filtered. These Gas sampling devices and additional units have due to blockages etc.

only have a limited service life and are therefore maintenance-active. For monitoring Qualified maintenance personnel are required for the system.

The object of the invention is to reduce the service life of filters to separate the solid fractions (dust, granulate, fibers, etc.) from To improve fluid flows significantly, especially the service life of automatic Emission and operational analysis equipment significantly improve the processing to simplify the fluid flows and make them as maintenance-free as possible.

This object is achieved according to the invention in that the to be separated Phase mixture is passed through a gap filter, which consists of a helical There is a helix, the slots between the individual windings acting as a sieve and the slot width by pulling apart or compressing the helix of is adjustable from the outside.

A preferred embodiment is characterized in that a) that the helix is installed between two pipe sections (inlet pipe and outlet pipe) and the fluid to be cleaned in continuous flow through the two pipe sections and is passed through the space enclosed by the helix, b) that the helix and at least a portion of the pipe sections of a concentric outer pipe having a Outlet for the filtered fluid is enclosed, which is fixed at one end with one of the two pipe sections and at the other end by means of a seal with the other Pipe section is connected, v c) and that means are available to the distance between the two pipe sections and thus the pitch of the helix to change between the limits hmin h (hmax.

A second embodiment especially suitable for gases is thereby characterized, a) that one side of the helix on the end face of an outer tube (Guide tube) and the other side via an end plate on one in the outer tube concentrically arranged, axially displaceable inner tube (gas sampling tube) is attached, b) that the inner tube is provided with openings in the area of the helix and is sealed against outside air and unfiltered gas, c) and that means are present in order to move the inner tube axially in the outer tube and thus to change the pitch of the helix between the limits hmin to h <hmax.

According to an expedient development of the invention is on Outlet for the filtered gas arranged a three-way valve.

This three-way cock is controlled so that the outlet is in position hmax (largest slot width) is connected to a flushing medium.

The helix is preferably made of an elastic material and has a spring characteristic, the spring being relaxed in position hmin is.

The means for adjusting the pitch h advantageously consist of a compressed air ring piston that transmits its movement to the moving tube. It must be ensured that the guides of the movable pipe against outside air are sealed.

These seals are expediently designed as sliding seals. Seals, which advantageously consist of a bellows, also show very good properties exist. The annular piston can also be replaced by a double-acting pressure piston which is firmly connected to the movable pipe. This one is preferred used for coils without spring characteristics.

The filter according to the invention has the advantage that it is less vulnerable is against solid deposits. Of particular importance is the possibility of easy agreement, without having to dismantle the filter. The filter is simply underneath for cleaning simultaneous pulling apart of the helix backwashed. The cleaning is still going to improved by the fact that the turns of the helix alternately hit one another and be pulled apart. Any stubborn dirt will be removed cut up and washed away. Another advantage is that the degree of separation of the filter can be set by changing the pitch h (pitch) can. This setting is made from the outside by means of the compressed air piston, without that something is changed in the filter construction itself. In contrast is With conventional screen and slot filters, the degree of separation through the mesh size fixed.

Embodiments of the invention are shown in the drawings and are described in more detail below. Figures 1a and 1b show the flow diagram how a helical coil filter works to remove dust and granules or fibrous particles from a liquid or process gas stream (Fig. 1a filter operation, Fig. 1b backwashing) and Figures 2a and 2b the flow diagram of the mode of operation of a helical rewind filter, used as a gas sampling probe for automatic gas analyzers, for removal the solid particles from the measuring gas (Fig. 2a filter operation, Fig. 2b backwashing).

Experience has shown that cleaning a filter by yourself is difficult Problem. A cleaning or cleaning of a sieve, net or the like can only be done with great forces are applied in order to guarantee safe working for a longer period of time to be able to. The part to be cleaned should therefore be as robust as possible. Eim Wendel can meet these conditions. It preferably consists of against the gas flows corrosion resistant high-alloy steels, possibly with provided with a plastic coating. By pulling the coil apart and backwashing it The filter can be cleaned with a solid-free flushing medium. By unique or knocking the helix together several times can have an additional backwash cleaning effect be achieved. In the compressed state hmin are located between the individual Windings of the coil only have small spaces for filtering the gas or liquid sstromes.

The mode of action of such a self-cleaning helical filter for Removal of dust, granules or fibrous particles from a liquid stream, is to be explained on the basis of a flow diagram (Fig. 1a and Ib). The same plant is also suitable for cleaning gas flows. In the following, however, the simplicity for the sake of speaking only of a "liquid flow". The helix 1 is here as a helical one Spring formed. It is attached with its ends to the pipe sections 5a and 4a. The pipe section 4a forms the liquid inlet, the pipe section 5a the liquid outlet. The filter housing 6 encloses the helix 1 and the as a concentric outer tube largest part of the inlet pipe 4a. The filter housing 6 is fixed on the outlet side connected to the outlet pipe 5a and has an outlet for the filtered liquid on. The filter housing 6 with a compressed air piston 7 stands in on the inlet side Link. By applying compressed air 9 to the cylinder 8 via the valve 10, the filter housing 6 moves relative to the inlet pipe 4a. The piston seal compared to the inlet pipe 4a can be improved by additional sliding seals 11 will.

The piston device 7, 8 can also be made by a commercially available one double-acting plunger are replaced, which is firmly connected to the outlet pipe 5a is. The inlet pipe 4 and the filter housing 6 must then have a flexible seal connected, e.g. a bellows. By actuating the piston, the coil changed between the limits hmin <h 'hmax will. The smallest Distance hmin is approx. 0.01 to 1 mm.

The greatest distance hmax between the turns is approx. 5 to 10 mm.

The liquid 3 flows through the helix 1 (state hmin) for min the inlet 4 and the outlet 5 continuously through the filter.

Conventional feed pumps can be used for transport.

Through the narrow slots between the individual turns 2 of the helix 1, the liquid is sucked off by the pump 13 via the three-way valve 12 and cleaned in the process. The purified liquid flows out through the outlet 14. she can can then be used again, e.g. fed back into the process. In the slots of the coil 1 are all larger particles of the liquid flow held back. The efficiency, i.e. the proportion of retained solids, can be adjusted to a certain extent by changing the spiral spacing.

Depending on the degree of contamination of the liquid, the Slits close after a while. To clean the slots, the coil 1 is pulled apart and backwashed with a rinsing liquid (Fig. Ib). This is done using the two-way valve 9 opened in the compressed air supply 10. This will put the over the filter housing 6 air pressure piston 7 rigidly connected to the drain pipe 5a and displaced the helix stretched (position hmaX). ). At the same time, the three-way valve 12 switches over and acts on the coil 1 with rinsing liquid. 15. The rinsing liquid 15 is combined with the continuously flowing process liquid discharged through the outlet 5. By releasing the helical spring once or several times (i.e. switching off the Compressed air) the individual turns of the spring collide and crush or cut up any residues of the solids that may still be present. With a helix without Spring action can do this with a second, oppositely acting compressed air piston can be achieved. After the backwash, the compressed air and the rinsing liquid flow switched off.

In both embodiments, the drain pipe 5 must be flexible Open the pipe, e.g. hose or bellows, since the drain pipe 5 together with the Filter housing 6 is movably arranged for flushing.

How a self-cleaning helical backwash filter works as a The gas sampling probe is to be explained with the aid of a flow diagram (Fig. 2a and 2b). The helix 1 is again designed as a helical spring. In a relaxed state (Fig. 2a) are only small between the individual turns 16 of the spring Gaps (0.01 - 0.1 mm) for filtering the gas. The uncleaned exhaust gas flows continuously past the filter. The sampling probe comes with a flange cover 17 brought directly into the exhaust gas flow at a suitable opening (flange) of a chimney. The helix 1 is rigidly connected to a guide tube 18. The other side of the Guide tube 18 is attached to the flange cover 17.

An end plate 19 serves to terminate the helix 1. This end plate 19 provides a rigid connection between the end face of the helix 1 and the gas sampling tube 20 ago. This gas sampling tube 20 is in the guide tube 18 with two gas-tight Guide rings 21 and 22 mounted movably in the direction of its axis. The gas sampling tube is in the area of the helix 1 with four parallel rows of openings 20 a pierced, so that a gaseous connection between the interior of the coil 1 and the interior of the gas sampling tube. For removing the from the helix Purified gas is this with a pump at the outlet 23 via the three-way valve 24 is pumped out through the gas sampling pipe 20. After the outlet 23 can still more Measurement gas conditioning devices, such as fine filtration, water vapor separation, etc.

follow. The helix 1 is almost completely compressed for the purpose of filtration (Position hmin). When using a helical spring min, this is relaxed. By the slots between the individual turns 16 of the coil 1 is due to the negative pressure sucked some exhaust gas and cleaned it. In the slots of the coil 1 are all larger particles of the exhaust gas (e.g. dust, soot, etc.) are retained. The efficiency, i.e. the proportion of solids retained is to some extent by changing the spiral spacing adjustable.

The slots are set according to the degree of pollution of the exhaust gas after some time to. To clean the slots, the coil 1 is pulled apart and backwashed with purge air.

For this purpose, the two-way valve 25 in the compressed air supply 26 is opened. As a result, the compressed air piston 27, which is rigidly connected to the guide tube 20, is displaced and the helix 1 expanded (position hmaX). The three-way valve switches at the same time 24 to and acts on the helix 1 with scavenging air 28. By one or more times Relaxation of the helical spring (i.e. switching off the compressed air with the two-way valve 25) the individual turns 16 of the helix 1 collide and loosen and crush any residues of the solids that may still be present. In the case of a helix without a spring effect this can be achieved with a second, oppositely acting compressed air piston. After backwashing, the compressed air with the two-way valve 25 and the scavenging air switched off with the three-way valve 24.

Claims (8)

Claims: 1. Backwash plate filter for removing solids in fluids, characterized in that the filter consists of a helical helix (1), the slots (2) between the individual turns as a sieve for the fluid (3) and the slot width (pitch h of the helix) act by pulling apart or compression of the coil (1) is adjustable from the outside. 2. Filter according to claim 1, characterized in that a) that the helix (1) is installed between two pipe sections (4a, 5a (inlet pipe and outlet pipe)) and the fluid (3) continuously through the two pipe sections (4a, 5a) and through the from the coil (1) enclosed space flows, b) that the coil (1) and at least a part of the pipe pieces (4a, 5a) of a concentric filter housing (6) with an outlet for the filtered fluid is enclosed which is fixed at one end with one (5a) of the two pipe sections and at the other end by means of a sliding Seal (11) is connected to the other pipe section (4a), c) and that means (7, 8) are available to the distance between the two pipe sections from each other and thus the To change the pitch of the helix (1) between the limits hmin <h h <hmaX. 3. Filter according to claim 1, in particular for filtering gases, characterized in that one side of the helix (1) on the end face of one Outer tube (guide tube 18 and the other side via an end plate (19) on one arranged concentrically in the outer tube (18) and displaceable in the axial direction Inner tube (20 (gas sampling tube)) is attached that the inner tube (20) in the area the coil (1) is provided with openings (20a) and against outside air and unfiltered gas is sealed and that means are provided to the inner tube (20) to move axially in the outer tube (18) and thus the pitch of the helix (1) to change between the limits hmin <h = hmaX. 4. Filter according to claim 2 to 3, characterized in that at the outlet a three-way cock (12, 24) is arranged for the filtered fluid and is controlled in this way is that the outlet is in position hmax (largest slot width of the helix) with a Inlet (15, 28) is connected for a flushing medium. 5. Filter according to claim 2 to 4, characterized in that the helix (1) is made of an elastic material and has a spring characteristic. 6. Filter according to claim 2 to 5, characterized in that the means to set the pitch h consist of a compressed air ring piston (7,8,27). 7. Filter according to claim 6, characterized in that the seal between the concentric filter housing (6) and one (4a) of the two pipe sections is designed as a sliding seal (11). 8. Filter according to claim 2 or 3, characterized in that the Seal between the concentric filter housing (6) and one (4a) of the two Pipe pieces is a bellows.